1) stone prison.. there is already this animation of being captured.. you can see it in one of the daedric prince quest which i will not spoil. so just like the prison comes out of the ground and you kneel and hold your head in dismay (i guess). make it stone bars with sharp spikes come out of the ground and imprison some enemy for..say.. 20 seconds.. and do damage to it over time.. because the bars are sharp.
hack.. make the bars go tighter and tighter, torturing and crushing the enemy!!!
2) another idea would be the ability to resurrect dead dragons, which are now bones. coz right now trying to do that makes the dragon's body shoot off into the sky.
3) a telekinesis like ability that works on living creatures. wouldn't it be awesome to hold some1 in the air.. maybe crushing him while you are at it with your telekinetic powah!
4) gravity shift- able to make it so your enemy falls to the ground and can't move or cancel it's gravity so you can hit it and it will fly away.. time to give those giants some payback

5) a spell that makes the target decay.. and if it dies b4 the spell runs out it explodes and infects all surrounding enemies with the same spell effect
6) underwater breathing and night eye spells coz i couldn't find them in the game which is just weird!
7) the ability to change your companion into a mount O_O
thats all i can think of at this hour.. its like 4am here